Defibrillating cardiac constraint

ABSTRACT

A device for treating cardiac disease of a heart includes a jacket of flexible material defining a volume between an open upper end and a lower end. The jacket is dimensioned for an apex of the heart to be inserted into the volume through the open upper end and for the jacket to be slipped over the heart. The jacket is adapted to be secured to the heart with the jacket having portions disposed on opposite sides of the heart. The jacket is adjustable to snugly conform to an external geometry of the heart and to constrain circumferential expansion of the heart during diastole and permit substantially unimpeded contraction of the heart during systole. A first and a second grid of electrodes are carried on the jacket. The grids are disposed to be in overlying relation to individual ones of the opposite sides of the heart when the jacket is secured to the heart. The first and second grids are connectable to a source of a defibrillating waveform

This application is a continuation of application Ser. No. 09/195,770,filed Nov. 18, 1998, now U.S. Pat. No. 6,169,922, which application(s)are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention pertains to a method for treating heart disease.More particularly, the present invention is directed to a method fortreating congestive heart disease and related valvular dysfunction andto provide defibrillating treatments.

2. Description of the Prior Art

Congestive heart disease is a progressive and debilitating illness. Thedisease is characterized by a progressive enlargement of the heart.

As the heart enlarges, the heart is performing an increasing amount ofwork in order to pump blood each heart beat. In time, the heart becomesso enlarged the heart cannot adequately supply blood. An afflictedpatient is fatigued, unable to perform even simple exerting tasks andexperiences pain and discomfort. Further, as the heart enlarges, theinternal heart valves cannot adequately close. This impairs the functionof the valves and further reduces the heart's ability to supply blood.

Causes of congestive heart disease are not fully known. In certaininstances, congestive heart disease may result from viral infections. Insuch cases, the heart may enlarge to such an extent that the adverseconsequences of heart enlargement continue after the viral infection haspassed and the disease continues its progressively debilitating course.

Patients suffering from congestive heart disease are commonly groupedinto four classes (i.e., Classes I, II, III and IV). In the early stages(e.g., Classes I and II), drug therapy is the commonly prescribedtreatment. Drug therapy treats the symptoms of the disease and may slowthe progression of the disease. Importantly, there is no cure forcongestive heart disease. Even with drug therapy, the disease willprogress. Further, the drugs may have adverse side effects.

Presently, the only permanent treatment for congestive heart disease isheart transplant. To qualify, a patient must be in the later stage ofthe disease (e.g., Classes III and IV with Class IV patients givenpriority for transplant). Such patients are extremely sick individuals.Class III patients have marked physical activity limitations and ClassIV patients are symptomatic even at rest.

Due to the absence of effective intermediate treatment between drugtherapy and heart transplant, Class III and IV patients will havesuffered terribly before qualifying for heart transplant. Further, aftersuch suffering, the available treatment is unsatisfactory. Hearttransplant procedures are very risky, extremely invasive and expensiveand only shortly extend a patient's life. For example, prior totransplant, a Class IV patient may have a life expectancy of 6 months toone-year. Heart transplant may improve the expectancy to about fiveyears.

Unfortunately, not enough hearts are available for transplant to meetthe needs of congestive heart disease patients. In the United States, inexcess of 35,000 transplant candidates compete for only about 2,000transplants per year. A transplant waiting list is about 8-12 monthslong on average and frequently a patient may have to wait about 1-2years for a donor heart. While the availability of donor hearts hashistorically increased, the rate of increase is slowing dramatically.Even if the risks and expense of heart transplant could be tolerated,this treatment option is becoming increasingly unavailable. Further,many patients do not qualify for heart transplant for failure to meetany one of a number of qualifying criteria.

Congestive heart failure has an enormous societal impact. In the UnitedStates alone, about five million people suffer from the disease (ClassesI through IV combined). Alarmingly, congestive heart failure is one ofthe most rapidly accelerating diseases (about 400,000 new patients inthe United States each year). Economic costs of the disease have beenestimated at $38 billion annually.

Not surprising, substantial effort has been made to find alternativetreatments for congestive heart disease. Recently, a new surgicalprocedure has been developed. Referred to as the Batista procedure, thesurgical technique includes dissecting and removing portions of theheart in order to reduce heart volume. This is a radical new andexperimental procedure subject to substantial controversy. Furthermore,the procedure is highly invasive, risky and expensive and commonlyincludes other expensive procedures (such as a concurrent heart valvereplacement). Also, the treatment is limited to Class IV patients and,accordingly, provides no hope to patients facing ineffective drugtreatment prior to Class IV. Finally, if the procedure fails, emergencyheart transplant is the only available option.

Clearly, there is a need for alternative treatments applicable to bothearly and later stages of the disease to either stop the progressivenature of the disease or more drastically slow the progressive nature ofcongestive heart disease. Unfortunately, currently developed options areexperimental, costly and problematic.

Cardiomyoplasty is a recently developed treatment for earlier stagecongestive heart disease (e.g., as early as Class III dilatedcardiomyopathy). In this procedure, the latissimus dorsi muscle (takenfrom the patient's shoulder) is wrapped around the heart and chronicallypaced synchronously with ventricular systole. Pacing of the muscleresults in muscle contraction to assist the contraction of the heartduring systole.

Even though cardiomyoplasty has demonstrated symptomatic improvement,studies suggest the procedure only minimally improves cardiacperformance. The procedure is highly invasive requiring harvesting apatient's muscle and an open chest approach (i.e., sternotomy) to accessthe heart. Furthermore, the procedure is expensive—especially thoseusing a paced muscle. Such procedures require costly pacemakers. Thecardiomyoplasty procedure is complicated. For example, it is difficultto adequately wrap the muscle around the heart with a satisfactory fit.Also, if adequate blood flow is not maintained to the wrapped muscle,the muscle may necrose. The muscle may stretch after wrapping reducingits constraining benefits and is generally not susceptible topost-operative adjustment. Finally, the muscle may fibrose and adhere tothe heart causing undesirable constraint on the contraction of the heartduring systole.

While cardiomyoplasty has resulted in symptomatic improvement, thenature of the improvement is not understood. For example, one study hassuggested the benefits of cardiomyoplasty are derived less from activesystolic assist than from remodeling, perhaps because of an externalelastic constraint. The study suggests an elastic constraint (i.e., anon-stimulated muscle wrap or an artificial elastic sock placed aroundthe heart) could provide similar benefits. Kass et al., ReverseRemodeling From Cardiomyoplasty In Human Heart Failure: ExternalConstraint Versus Active Assist, 91 Circulation 2314-2318 (1995).Similarly, cardiac binding is described in Oh et al., The Effects ofProsthetic Cardiac Binding and Adynamic Cardiomyoplasty in a Model ofDilated Cardiomyopathy, 116 J. Thorac. Cardiovasc. Surg. 148-153 (1998),Vaynblat et al., Cardiac Binding in Experimental Heart Failure, 64 Ann.Thorac. Surg. 81-85 (1997) and Capouya et al., Girdling Effect ofNonstimulated Cardiomyoplasty on Left Ventricular Function, 56 Ann.Thorac. Surg. 867-871 (1993).

In addition to cardiomyoplasty, mechanical assist devices have beendeveloped as intermediate procedures for treating congestive heartdisease. Such devices include left ventricular assist devices (“LVAD”)and total artificial hearts (“TAH”). An LVAD includes a mechanical pumpfor urging blood flow from the left ventricle into the aorta Suchsurgeries are expensive. The devices are at risk of mechanical failureand frequently require external power supplies. TAH devices are used astemporary measures while a patient awaits a donor heart for transplant.

Commonly assigned U.S. Pat. No. 5,702,343 to Alferness dated Dec. 30,1997 teaches a jacket to constrain cardiac expansion during diastole.Also, PCT International Publication No. WO 98/29401 published Jul. 9,1998 teaches a cardiac constraint in the form of surfaces on oppositesides of the heart with the surfaces joined together by a cable throughthe heart or by an external constraint. U.S. Pat. No. 5,800,528 datedSep. 1, 1998 teaches a passive girdle to surround a heart.

Patients suffering from congestive heart failure are frequentlyvulnerable to additional cardiac risks. For example, cardiac arrhythmiascan arise. Defibrillation is a method to terminate fibrillation. Asdisclosed in commonly assigned and copending U.S. patent applicationSer. No. 09/114,757 filed Jul. 13, 1998, a cardiac constraint device ispreferably electrically permeable to permit application of an externallysourced defibrillating waveform. The prior art includes implantabledefibrillators. An example of such an implantatable defibrillation isshown in European Patent Application No. 88301663.6 published Aug. 31,1988 as Publication No. 0 280 564 A2. One object of the presentinvention to provide a cardiac constraint device which can also performdefibrillating functions.

SUMMARY OF THE INVENTION

According to a preferred embodiment of the present invention, a deviceis disclosed for treating cardiac disease of a heart. The deviceincludes a jacket of flexible material defining a volume between an openupper end and a lower end of the jacket. The jacket is dimensioned foran apex of the heart to be inserted into the volume through the openupper end and for the jacket to be slipped over the heart. The jackethas a longitudinal dimension between the upper and lower ends sufficientfor the jacket to constrain the lower portion of the heart between avalvular annulus and ventricular lower extremities. The jacket isadapted to be secured to the heart with the jacket having portionsdisposed on opposite sides of the heart between the valvular annulus andthe ventricular lower extremities. The jacket is adjustable to snuglyconform to an external geometry of the heart and to constraincircumferential expansion of the heart during diastole and permitsubstantially unimpeded contraction of the heart during systole. In oneembodiment, a first and a second grid electrode is carried on thejacket. The grids are disposed to be in overlying relation to oppositesides of the heart when the jacket is secured to the heart. The firstand second grids are connectable to a source of a defibrillatingwaveform.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of a normal, healthy humanheart shown during systole;

FIG. 1A is the view of FIG. 1 showing the heart during diastole;

FIG. 1B is a view of a left ventricle of a healthy heart as viewed froma septum and showing a mitral valve;

FIG. 2 is a schematic cross-sectional view of a diseased human heartshown during systole;

FIG. 2A is the view of FIG. 2 showing the heart during diastole;

FIG. 2B is the view of FIG. 1B showing a diseased heart;

FIG. 3 is a perspective view of a cardiac constraint device to be usedaccording to the method of the present invention;

FIG. 3A is a side elevation view of a diseased heart in diastole withthe device of FIG. 3 in place;

FIG. 4 is a perspective view of an alternative cardiac constraint deviceto be used according to the method of the present invention;

FIG. 4A is a side elevation view of a diseased heart in diastole withthe device of FIG. 4 in place;

FIG. 5 is a cross-sectional view of the device of FIG. 3 overlying amyocardium and with the material of the device gathered for a snug fit;

FIG. 6 is an enlarged view of a knit construction of the device of thepresent invention in a rest state;

FIG. 7 is a schematic view of the material of FIG. 6;

FIG. 8 is a view of the device of FIG. 3 secured to a heart and modifiedaccording to the teachings of the present invention; and

FIG. 9 is a view of the open cell material of the jacket of FIG. 8 andshowing interwoven defibrillating conductors of an electrode grid.

DESCRIPTION OF THE PREFERRED EMBODIMENT A. Congestive Heart Failure

To facilitate a better understanding of the present invention,description will first be made of a cardiac constraint device such as ismore fully described in commonly assigned and copending U.S. patentapplication Ser. No. 09/114,757 filed Jul. 13, 1998. In the drawings,similar elements are labeled similarly throughout.

With initial reference to FIGS. 1 and 1A, a normal, healthy human heartH′ is schematically shown in cross-section and will now be described inorder to facilitate an understanding of the present invention. In FIG.1, the heart H′ is shown during systole (i.e., high left ventricularpressure). In FIG. 1A, the heart H′ is shown during diastole (i.e., lowleft ventricular pressure).

The heart H′ is a muscle having an outer wall or myocardium MYO′ and aninternal wall or septum S′. The myocardium MYO′ and septum S′ definefour internal heart chambers including a right atrium RA′, a left atriumLA′, a right ventricle RV′ and a left ventricle LV′. The heart H′ has alength measured along a longitudinal axis BB′-AA′ from an upper end orbase B′ to a lower end or apex A′.

The right and left atria RA′, LA′ reside in an upper portion UP′ of theheart H′ adjacent the base B′. The right and left ventricles RV′, LV′reside in a lower portion LP′ of the heart H′ adjacent the apex A′. Theventricles RV′, LV′ terminate at ventricular lower extremities LE′adjacent the apex A′ and spaced therefrom by the thickness of themyocardium MYO′.

Due to the compound curves of the upper and lower portions UP′, LP′, theupper and lower portions UP′, LP′ meet at a circumferential groovecommonly referred to as the A-V groove AVG′. Extending away from theupper portion UP′ are a plurality of major blood vessels communicatingwith the chambers RA′, RV′, LA′, LV′. For ease of illustration, only thesuperior vena cava SVC′, inferior vena cava IVC′ and a left pulmonaryvein LPV′ are shown as being representative.

The heart H′ contains valves to regulate blood flow between the chambersRA′, RV′, LA′, LV′ and between the chambers and the major vessels (e.g.,the superior vena cava SVC′, inferior vena cava IVC′ and a leftpulmonary vein LPV′). For ease of illustration, not all of such valvesare shown. Instead, only the tricuspid valve TV′ between the rightatrium RA′ and right ventricle RV′ and the mitral valve MV′ between theleft atrium LA′ and left ventricle LV′ are shown as beingrepresentative.

The valves are secured, in part, to the myocardium MYO′ in a region ofthe lower portion LP′ adjacent the A-V groove AVG′ and referred to asthe valvular annulus VA′. The valves TV′ and MV′ open and close throughthe beating cycle of the heart H.

FIGS. 1 and 1A show a normal, healthy heart H′ during systole anddiastole, respectively. During systole (FIG. 1), the myocardium MYO′ iscontracting and the heart assumes a shape including a generally conicallower portion LP′. During diastole (FIG. 1A), the heart H′ is expandingand the conical shape of the lower portion LP′ bulges radially outwardly(relative to axis AA′-BB′).

The motion of the heart H′ and the variation in the shape of the heartH′ during contraction and expansion is complex. The amount of motionvaries considerably throughout the heart H′. The motion includes acomponent which is parallel to the axis AA′-BB′ (conveniently referredto as longitudinal expansion or contraction). The motion also includes acomponent perpendicular to the axis AA′-BB′ (conveniently referred to ascircumferential expansion or contraction).

Having described a healthy heart H′ during systole (FIG. 1) and diastole(FIG. 1A), comparison can now be made with a heart deformed bycongestive heart disease. Such a heart H is shown in systole in FIG. 2and in diastole in FIG. 2A. All elements of diseased heart H are labeledidentically with similar elements of healthy heart H′ except only forthe omission of the apostrophe in order to distinguish diseased heart Hfrom healthy heart H′.

Comparing FIGS. 1 and 2 (showing hearts H′ and H during systole), thelower portion LP of the diseased heart H has lost the tapered conicalshape of the lower portion LP′ of the healthy heart H′. Instead, thelower portion LP of the diseased heart H bulges outwardly between theapex A and the A-V groove AVG. So deformed, the diseased heart H duringsystole (FIG. 2) resembles the healthy heart H′ during diastole (FIG.1A). During diastole (FIG. 2A), the deformation is even more extreme.

As a diseased heart H enlarges from the representation of FIGS. 1 and 1Ato that of FIGS. 2 and 2A, the heart H becomes a progressivelyinefficient pump. Therefore, the heart H requires more energy to pumpthe same amount of blood. Continued progression of the disease resultsin the heart H being unable to supply adequate blood to the patient'sbody and the patient becomes symptomatic of cardiac insufficiency.

For ease of illustration, the progression of congestive heart diseasehas been illustrated and described with reference to a progressiveenlargement of the lower portion LP of the heart H. While suchenlargement of the lower portion LP is most common and troublesome,enlargement of the upper portion UP may also occur.

In addition to cardiac insufficiency, the enlargement of the heart H canlead to valvular disorders. As the circumference of the valvular annulusVA increases, the leaflets of the valves TV and MV may spread apart.After a certain amount of enlargement, the spreading may be so severethe leaflets cannot completely close. Incomplete closure results invalvular regurgitation contributing to an additional degradation incardiac performance. While circumferential enlargement of the valvularannulus VA may contribute to valvular dysfunction as described, theseparation of the valve leaflets is most commonly attributed todeformation of the geometry of the heart H.

B. Cardiac Constraint Therapy

Having described the characteristics and problems of congestive heartdisease, a treatment method and apparatus are described in commonlyassigned and copending U.S. patent application Ser. No. 09/114,757 filedJul. 13, 1998 now U.S. Pat. No. 6,085,754. In general, a jacket isconfigured to surround the myocardium MYO. While the method of thepresent invention will be described with reference to a jacket asdescribed in commonly assigned and copending U.S. patent applicationSer. No. 09/114,757 filed Jul. 13, 1998, now U.S. Pat. No. 6,085,754 itwill be appreciated the present invention is applicable to any cardiacconstraint device including those shown in U.S. Pat. No. 5,800,528 andPCT International Publication No. WO 98/29401.

With reference now to FIGS. 3, 3A, 4 and 4A, the cardiac constraintdevice is shown as a jacket 10, 10′ of flexible, biologically compatiblematerial. The jacket 10 is an enclosed knit material having upper andlower ends 12, 12′, 14, 14′. The jacket 10, 10′ defines an internalvolume 16, 16′ which is completely enclosed but for the open ends 12,12′ and 14′. In the embodiment of FIG. 3, lower end 14 is closed. In theembodiment of FIG. 4, lower end 14′ is open. In both embodiments, upperends 12, 12′ are open. Throughout this description, the embodiment ofFIG. 3 will be discussed. Elements in common between the embodiments ofFIGS. 3 and 4 are numbered identically with the addition of anapostrophe to distinguish the second embodiment and such elements neednot be separately discussed.

The jacket 10 is dimensioned with respect to a heart H to be treated.Specifically, the jacket 10 is sized for the heart H to be constrainedwithin the volume 16. The jacket 10 can be slipped around the heart H.The jacket 10 has a length L between the upper and lower ends 12, 14sufficient for the jacket 10 to constrain the lower portion LP. Theupper end 12 of the jacket 10 extends at least to the valvular annulusVA and further extends to the lower portion LP to constrain at least thelower ventricular extremities LE.

When the parietal pericardium is opened, the lower portion LP is free ofobstructions for applying the jacket 10 over the apex A. If, however,the parietal pericardium is intact, the diaphragmatic attachment to theparietal pericardium inhibits application of the jacket over the apex Aof the heart. In this situation, the jacket can be opened along a lineextending from the upper end 12′ to the lower end 14′ of jacket 10′. Thejacket can then be applied around the pericardial surface of the heartand the opposing edges of the opened line secured together after placedon the heart. Systems for securing the opposing edges are disclosed in,for example, U.S. Pat. No. 5,702,343, the entire disclosure of which isincorporated herein by reference. The lower end 14′ can then be securedto the diaphragm or associated tissues using, for example, sutures,staples, etc.

In the embodiment of FIGS. 3 and 3A, the lower end 14 is closed and thelength L is sized for the apex A of the heart H to be received withinthe lower end 14 when the upper end 12 is placed at the A-V groove AVG.In the embodiment of FIGS. 4 and 4A, the lower end 14′ is open and thelength L′ is sized for the apex A of the heart H to protrude beyond thelower end 14′ when the upper end 12′ is placed at the A-V groove AVG.The length L′ is sized so that the lower end 14′ extends beyond thelower ventricular extremities LE such that in both of jackets 10, 10′,the myocardium MYO surrounding the ventricles RV, LV is in directopposition to material of the jacket 10, 10′. Such placement isdesirable for the jacket 10, 10′ to present a constraint againstenlargement of the ventricular walls of the heart H.

After the jacket 10 is positioned on the heart H as described above, thejacket 10 is secured to the heart. Preferably, the jacket 10 is securedto the heart H through sutures. The jacket 10 is sutured to the heart Hat suture locations S circumferentially spaced along the upper end 12.While a surgeon may elect to add additional suture locations to preventshifting of the jacket 10 after placement, the number of such locationsS is preferably limited so that the jacket 10 does not restrictcontraction of the heart H during systole.

To permit the jacket 10 to be easily placed on the heart H, the volumeand shape of the jacket 10 are larger than the lower portion LP duringdiastole. So sized, the jacket 10 may be easily slipped around the heartH. Once placed, the jacket's volume and shape are adjusted for thejacket 10 to snugly conform to the external geometry of the heart Hduring diastole. Such sizing is easily accomplished due to the knitconstruction of the jacket 10. For example, excess material of thejacket 10 can be gathered and sutured S″ (FIG. 5) to reduce the volumeof the jacket 10 and conform the jacket 10 to the shape of the heart Hduring diastole. Such shape represents a maximum adjusted volume. Thejacket 10 constrains enlargement of the heart H beyond the maximumadjusted volume while preventing restricted contraction of the heart Hduring systole. As an alternative to gathering of FIG. 5, the jacket 10can be provided with other arrangements for adjusting volume. Forexample, as disclosed in U.S. Pat. No. 5,702,343, the jacket can beprovided with a slot. The edges of the slot can be drawn together toreduce the volume of the jacket.

The jacket 10 is adjusted to a snug fit on the heart H during diastole.Care is taken to avoid tightening the jacket 10 too much such thatcardiac function is impaired. During diastole, the left ventricle LVfills with blood. If the jacket 10 is too tight, the left ventricle LVcannot adequately expand and left ventricular pressure will rise. Duringthe fitting of the jacket 10, the surgeon can monitor left ventricularpressure. For example, a well-known technique for monitoring so-calledpulmonary wedge pressure uses a catheter placed in the pulmonary artery.The wedge pressure provides an indication of filling pressure in theleft atrium LA and left ventricle LV. While minor increases in pressure(e.g., 2-3 mm Hg) can be tolerated, the jacket 10 is snugly fit on theheart H but not so tight as to cause a significant increase in leftventricular pressure during diastole.

As mentioned, the jacket 10 is constructed from a knit, biocompatiblematerial. One embodiment of the knit 18 is illustrated in FIG. 6.Preferably, the knit is a so-called “Atlas knit” well known in thefabric industry. The Atlas knit is described in Paling, Warp KnittingTechnology, p. 111, Columbine Press (Publishers) Ltd., Buxton, GreatBritain (1970).

The Atlas knit is a knit of fibers 20 having directional expansionproperties. More specifically, the knit 18, although formed of generallyinelastic fibers 20, permits a construction of a flexible fabric atleast slightly expandable beyond a rest state. FIG. 6 illustrates theknit 18 in a rest state. The fibers 20 of the fabric 18 are woven intotwo sets of fiber strands 21 a, 21 b having longitudinal axes X_(a) andX_(b). The strands 21 a, 21 b are interwoven to form the fabric 18 withstrands 21 a generally parallel and spaced-apart and with strands 21 bgenerally parallel and spaced-apart.

For ease of illustration, fabric 18 is schematically shown in FIG. 7with the axis of the strands 21 a, 21 b only being shown. The strands 21a, 21 b are interwoven with the axes X_(a) and X_(b) defining adiamond-shaped open cell 23 having diagonal axes A_(m). In a preferredembodiment, the axes A_(m) are 5 mm in length when the fabric 18 is atrest and not stretched. The fabric 18 can stretch in response to aforce. For any given force, the fabric 18 stretches most when the forceis applied parallel to the diagonal axes A_(m). The fabric 18 stretchesleast when the force is applied parallel to the strand axes X_(a) andX_(b). The jacket 10 is constructed for the material of the knit to bedirectionally aligned for a diagonal axis A_(m) to be parallel to theheart's longitudinal axis AA-BB

While the jacket 10 is expandable due to the above-described knitpattern, the fibers 20 of the knit 18 are preferably non-expandable.While all materials expand to at least a small amount, the fibers 20 arepreferably formed of a material with a low modulus of elasticity. Inresponse to the low pressures in the heart H during diastole, the fibers20 are non-elastic. In a preferred embodiment, the fibers are 70 Denierpolyester. While polyester is presently preferred, other suitablematerials include polytetrafluoroethylene (PTFE), expanded PTFE (ePTFE)or polypropylene.

The knit material has numerous advantages. Such a material is flexibleto permit unrestricted movement of the heart H (other than the desiredconstraint on circumferential expansion). The material is open defininga plurality of interstitial spaces for fluid permeability as well asminimizing the amount of surface area of direct contact between theheart H and the material of the jacket 10 (thereby minimizing areas ofirritation or abrasion) to minimize fibrosis and scar tissue.

The open areas of the knit construction also allows for electricalconductivity between the heart and surrounding tissue for passage ofelectrical current to and from the heart. For example, although the knitmaterial is an electrical insulator, the open knit construction issufficiently electrically permeable to permit the use of trans-chestdefibrillation of the heart. Also, the open, flexible constructionpermits passage of electrical elements (e.g., pacer leads) through thejacket. Additionally, the open construction permits other procedures,e.g., coronary bypass, to be performed without removal of the jacket.

A large open area for cells 23 is desirable to minimize the amount ofsurface area of the heart H in contact with the material of the jacket10 (thereby reducing fibrosis). However, if the cell area 23 is toolarge, localized aneurysm can form. Also, a strand 21 a, 21 b can overlya coronary vessel with sufficient force to partially block the vessel. Asmaller cell size increases the number of strands thereby decreasing therestricting force per strand. Preferably, a maximum cell area is nogreater than about 6.45 cm² (about 2.54 cm by 2.54 cm) and, morepreferably, is about 0.25 cm² (about 0.5 cm by 0.5 cm). The maximum cellarea is the area of a cell 23 after the material of the jacket 10 isfully stretched and adjusted to the maximum adjusted volume on the heartH as previously described.

The fabric 18 is preferably tear and run resistant. In the event of amaterial defect or inadvertent tear, such a defect or tear is restrictedfrom propagation by reason of the knit construction.

The jacket 10 constrains further undesirable circumferential enlargementof the heart while not impeding other motion of the heart H. With thebenefits of the present teachings, numerous modifications are possible.For example, the jacket 10 need not be directly applied to theepicardium (i.e., outer surface of the myocardium) but could be placedover the parietal pericardium. Further, an anti-fibrosis lining (such asa PTFE coating on the fibers of the knit) could be placed between theheart H and the jacket 10. Alternatively, the fibers 20 can be coatedwith PTFE.

The jacket 10 can be used in early stages of congestive heart disease.For patients facing heart enlargement due to viral infection, the jacket10 permits constraint of the heart H for a sufficient time to permit theviral infection to pass. In addition to preventing further heartenlargement, the jacket 10 treats valvular disorders by constrainingcircumferential enlargement of the valvular annulus and deformation ofthe ventricular walls.

C. Defibrillation Therapy

FIG. 8 illustrates the device of FIG. 3 modified according to thepresent invention. In FIG. 8, an open cell jacket 10 of knitconstruction as previously described is placed on a heart H. The jacket10 carries first and second electrode grids 100, 100 a of electrodeconductors 101, 101 a. The conductors 101, 101 a are bundled ininsulated carriers 104, 104 a. The carriers 104, 104 a convey theconductors 101, 101 a to an implantable source 106 of a defibrillatingwaveform.

FIG. 9 illustrates how the first grid 100 is incorporated into thematerial 18 of the jacket 10. Since second grid 100 a is similarlyincorporated, it is not separately shown and described in detail.

As previously described, the material 18 is a knit definingcrisscrossing fiber strands 21 a, 21 b. The strands 21 a, 21 b define agrid of open cells 23. Uninsulated, electrically conductive electrodeconductors 101 are interwoven through the cells 23. Examples of suchelectrode conductors 101 include titanium wire and platinum-coatedstainless steel. Such electrode conductors 101 may be braided,multi-strand wires.

In one undulating pattern, the electrode conductors 101 are woven intoalternating ones of the strands 21 a, 21 b. For example, an electrodeconductor 101 may be woven into strand 21 b for a distance equal to thelength of two cells 23. Then, the electrode conductor 101 is woven intostrand 21 a for a distance equal to the length of two cells 23. Thiscreates a zigzag pattern repeated along the length of the electrodeconductor 101. For ease of illustration, FIG. 9 shows strands 21 a, 21 bas monofilament strands with conductors 101 positioned alongside thestrands 21 a, 21 b. In fact, strands 21 a, 21 b are preferablymultifilament as illustrated in FIG. 6 and the conductors 101 areinterwoven into the multifilaments to securely position the conductors101 on the jacket 10 and to maintain spacing between adjacent conductors101.

The electrode conductors 101 extend in a direction parallel to thelongitudinal axis of the heart. Opposing electrode conductors 101 areevenly spaced along their length.

The grids 100, 100 a are positioned on the jacket 10 to overly oppositesides of the heart H after placement of the jacket 10 over the heart.Preferably, the grids 100, 100 a overly the right and left lateralventricular epicardium, respectively. As a result, a maximum amount ofcardiac mass is located within the direct current path of adefibrillating shock.

As the jacket 10 is adjusted during placement, the cell size may very.Due to the jacket construction as described, the cell size around acircumference of the heart remains uniform. Therefore, during adjustmentof the jacket, a uniform spacing between electrode conductors 101, 101 ais retained.

With the construction as described, a defibrillating shock can readilybe applied to a patient's heart treated with a cardiac constraintdevice. Further, the jacket 10 retains its electrical permeable qualitypermitting additional defibrillation applied external to the body. Indefibrillators, the electrode conductors also act to receive signalsfrom the heart. Since the electrode conductors are in close proximity tothe heart, these electrode conductors permit easy detection of cardiacsignals by the implantable defibrillator 106 facilitating analysis ofelectrical activity of the heart.

From the foregoing detailed description, the invention has beendescribed in a preferred embodiment. Modifications and equivalents ofthe disclosed concepts are intended to be included within the scope ofthe appended claims. For example, the fibers 21 a, 21 b of the jacketmaterial 18 may be selectively metalized with such fibers serving as theelectrode conductors. Also, while the invention is shown overlying theventricles, the jacket may overly the atria with grids over the atria todefibrillate the atria.

What is claimed is:
 1. A method for treating cardiac disease of apatient's heart, said method comprising: surgically accessing saidpatient's heart and diaphragm; placing a jacket around said heart, saidjacket comprising a biomedical material of an open cell constructionhaving an upper end and a lower end, said jacket adapted to be securedto said heart with said jacket having portions disposed on oppositesides of said heart between said valvular annulus and said ventricularlower extremities, a first and second electrode grid comprisingconductors interwoven through open cells of said jacket material andconnected to a source of a defibrillating waveform; adjusting andsecuring said jacket on said heart to snugly conform to said externalgeometry of said heart to constrain circumferential expansion of saidheart during diastole and permitting unimpeded contraction of said heartduring systole and with said first and second electrode grids disposedin overlying relation to said opposite sides of said heart; applying adefibrillating electrical waveform to said grids.
 2. A method accordingto claim 1 wherein said conductors extend in a line substantiallyparallel to said longitudinal axis.
 3. A method according to claim 1wherein said conductors of one of said grids are evenly spaced apart. 4.A method according to claim 1 further comprising a step of gatheringexcess amounts of said material following placement of said jacket oversaid heart to snugly conform said material to said external geometry ofsaid heart.